For the automatic insertion of components on circuit boards, the components are withdrawn from a pick-up location on a component feeding device by using a gripping device and are transported to the component insertion location on the circuit board.
The term component in the following is understood to mean all elements that can be assembled, in particular electronic components, electromechanical components, plugs and plug connections for electrical and mechanical contacts, as well as shields made of sheet metal. Elements for insertion furthermore are bare dies or individual parts of a semiconductor wafer that are further processed into complete components following the structuring and cutting of the wafer.
Suction pipettes arranged on an insertion head, in particular, can be used as gripping devices and can be connected to a vacuum system. With the aid of these suction pipettes, the components for insertion can be picked up without interruption from the component feeding device, can be transported reliably to the desired insertion location and can be released there at an exactly defined placement location. To achieve the highest possible insertion rate with modern automatic insertion machines, the pickup of components from the component feeding device, the transport and the insertion of these components on the substrates must occur as quickly as possible. At the same time, however, damage to the component, the gripping device and the substrate is to be avoided at all cost.
The components for insertion, which are suspended vertically from the top by the suction pipettes, can be damaged, for example, through a high impact when they are place with excessive speed onto the substrates. In particular since the substrate position can diverge significantly, for example through bulging, corresponding measures must be taken to prevent the gripping device and the component for insertion from hitting the substrate with excessive speed.
For this, the U.S. Pat. No. 5,285,946 discloses a device for placing electronic components onto the surfaces of circuit boards. With this device, a suction pipette tip that functions as gripping device is positioned with spring force. The spring force ensures that the necessary contact pressure is reached when the component is placed onto the substrate or when the suction pipette is attached to the component in a component-feeding device, without destroying the component as a result of excessive pressure or an excessive impact. This solution increases the susceptibility of the gripper as well as its mass and reduces the positioning accuracy that can be achieved.
Another known option for avoiding damage to the components to be inserted and, at the same time, achieve a relatively high insertion capacity is to move the components at a slower speed just prior to the insertion, following an initially high transport movement, so that the impact between the component and the substrate is not excessive. A high insertion capacity at the cost of a higher error rate is achieved by maintaining a fast transport movement until just prior to reaching the substrate for insertion. A low probability of insertion errors is achieved by reducing the fast transport speed early enough so that an excessively hard impact of the component during the insertion can reliably be avoided. Thus, the automatic insertion of components always requires a compromise between the highest possible insertion speed on the one hand and the lowest possible insertion error rate caused by excessive impact.